Polycentric articulated finger for artificial hands



L. J. PARKER 2,598,593

2 swam-swam 1 POLYCENTRIC ARTICULATED FINGER FOR ARTIFICIAL HANDSINVENTOR LINUS J. PARKER flue-L Ki wa AGENT May 27, 1952 Filed Sept. 30,1948 May 27, 1952 PARKER 4 2,598,593

POLYCENTRIC ARTICULATED FINGER F'QR ARTIFICIAL HANDS Filed Sept. 50,1948 j 2 SHEETS-SHEET 2 VENTOR LIN J. PARKER BY c M 3.0mm

AGENT Patented May 27, 1952 UNITED STATES ATENT OFFICE POLYCENTRICARTICULATED FINGER FOR ARTIFICIAL HANDS Linus J. Parker, Windsor, N. Y.,assignor to International Business Machines Corporation,

6 Claims.

The improved polycentric articulated finger comprising the presentinvention has been designed primarily for use in connection with thehand section of the electrically driven artificial arm.

The, articulated finger is, however, capable of being employed inconnection with other types of artificial hands and when so employed anyone of the five fingers of the hand, with the exception of the thumb,may embody the principles of the present invention.

It is among the principal objects of the present invention to provide anarticulated finger comprising a proximal segment, a medial segment and adistal or tip segment, which segments are formed by a moulding processwith the proximal and distal segments having concave ends, while themedial segment is provided With matching convex ends. The segments arehingedly secured together so as to be capable of rolling around on eachother, so to speak, while a relatively constant and small separationline is maintained between the segments.

In carrying out the invention, the joints between the segments areformed by male projections on the proximal and distal segments whichWork smoothly within the female ends of the medial segment. Thus ampleresistance to side thrust is given by the material itself minimizing thestresses upon the bearings. The segments are joined by steel bushingswhich make a running fit with the outer walls of the segments by forminga pressed fit with the inner walls or projections. The material of thevarious segments is preferably mouldable nylon on account of thestrength and durability of the latter and also because of the ease withwhich the material may be tinted to resemble the color of human flesh.Articulation is produced by a combination of a lever linkage and a pairof mating gear sectors which span the medial joint. These gears are outdirectly in the nylon projections of the proximal and distal segments.The articulations of the finger segments are related to the flexion ofthe proximal joint by a steel bracket which is attached to the frame ofthe hand section. When the proximal segment is flexed a pivoted linkageacting between the bracket and the medial segments forces the latter torotate with respect to the proximal segment. This rotation carries agear sector on the distal segment around a gear sector on the proximalsegment, thus causing the distal segment or tip of the finger to curlinward at a uniform rate with the entire finger closely simulating-thenormal curling action of a natural finger.

Other objects or the invention will be pointed out in the followingdescription and claims and illustrated in the accompanyin drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a side elevational view of an articulated finger constructedin accordance with the principles of the present invention. This view issomewhat diagrammatic in its representation and illustrates an extendedand a retracted or curled position of the finger.

Fig. 2 is a sectional view taken substantially along the line 2-2 ofFig. 1 in the direction indicated by the arrows.

Fig. 3 is a sectional view taken substantially along the line 33 of Fig.2.

Fig. 4 is a sectional View taken substantially along the line 4--4 ofFig. 3.

Fig. 5 is a sectional view taken substantially along the line 55 of Fig.2.

Fig. 6 is a sectional view taken substantially along the line 6-6 ofFig. 2.

In all of the above described views like characters of reference areemployed to designate like parts throughout.

Referring now to the drawings in detail, the articulated finger involvesin its general organization a proximal segment ill, a medial segment l2,and a distal or tip segment I4, each of these segments being formed by amoulding process, the material preferably being nylon on account of theruggedness and durability of the latter and the fact that the same mayreadily be colored to simulate the natural appearance of the human handby a dyeing process.

The proximal segment in is in the form of a hollow shell having agenerally rounded end l6 Which is adapted to fit snugly Within a recessprovided in the shell I! of the hand section of the artificial arm (notshown). The segment I0 is provided with a pair of inwardly extending hubportions I8 and 28 (Figs. 2 and 3) through which there projects astainless steel pivot pin 22, which pin may form the common pivotalsupport for a series of the articulated fingers, only one such fingerbeing shown in the drawings. The pin 22 has its end suitably supportedin a portion (not shown) of the frame 23 of the hand section of theartificial arm. A metal hub 24 surrounds the pin 22 between the hubs l8and 20 and is integrally formed with an attachment bracket 26 whichprojects through a slot 28 provided in the end It of the segment I0 andwhich is provided with a laterally turned end 33 having an attachmenthole or opening 3!! formed therein designed for reception of anattachment screw 29, by means of which the bracket 25 is fixedly securedto the frame 23 of the hand section of the artificial arm.

The segment ID is formed at its outer end with a centrally disposed gearsector 32 having a series of gear teeth 34 (Figs. 2 and 3) formedthereon. The sides of the shell of which the segment I0 is formed, arecut away as at 36 on opposite sides of the gear sector 32, thesecut-away portions being of arcuate configuration to permit nesting 3 ofthe innerend of thefinger segment I2 within the outer end of the segment[0. The segment I2 is provided with a pair of internal hub portions 38and 40 through which there extends a hollow tubular pintle pin 42' whichextends other end of the link being pivotally secured to.

the segment 12 by means of a pin Eiii which. project's through a curvedslot 52 formed in the gear sector 32' and which has its ends extendinginto.

and secured in the sides of the shell of which. the

segment i2 is formed. The internal hub portion iil'of the finger segmenti2v is cut away as at 55 V to' provide a clearance for the pin 53 andvthe end of the. link 43. V The distal. or tip segment. I4

is provided with a centrall disposed gear. sector M EBhaving a series ofteeth 58'formed' thereon designed for meshing engagement with. the teeth34 of the gear sector 32. The inner end. of the sides of the shell ofwhich the hollow finger segment is is formed is cut away as at 6?! onopposite sides of the sector as to permit. the curved. outer endof thefinger segment l2 to be nested: within the innerend of the shell of thesegment is. A hollow pintle pin 62' has its ends secured in the sides ofthe shell of the segment I? and passes through an opening 84' formed. inthe gear sector E E. A pair of nylon plugs 86, similar to the plugs 44',seal the ends of the hollow pintle pin 62.

It will be seen from'the above description of parts that because theouter end of the link 68 is secured tothe' sides of the. shell of thefinger segment [2 at a point which is eccentrically disposed withrespect to the pintle pin 42, counterclockwise rotational movement ofthe finger. segment i9 relative to the. fixed bracket 28, as shown inFig. 3, will apply a torque to the finger segirier 2 tending to causethis latter segment to move relative to the segment H3 in acounterclockwise direction. This phenomenon of mutual interdependency ofmovement between the two segments i8 and 2 exists by virtue of the factthat while the distance between the axes of the pintle pins 22 and' iiremains the same dur ing swinging movement of the finger segment It, thedistance between the axis of the pintie pin 22 and the axisof the pivotpin 59 becomes shorter. This latter pivot pin efl, being eccentric withrespect to the pintlepin 52, will cause the link 38 to exert a pullingtorque on the shell of the finger segment #2 to decrease the anglebetween the longitudinal axes of the two segments H3 and i2 directproportion to the extent of pivotal movement of the segment i 0 aboutthe axis of the bracket 25. Because of. the fact that the distancebetween theaxes'of the pintle pins 12 and 51? remains constant, tiltingmovement of thesegmen-t l2 relative to-thesegment to in acounterclockwise direction, as viewed in Fig. 2, will cause the gearsector 55 to roll on the gear sector 32, thus moving the segment itabout the axis of the pintle pin ea in 'a counter-clockwise directionrelative to the segment 12, so that the three finger segments Hi, i2 andI4 assume a progressive curling action as illustrated by the dotted lineconfiguration of these segments.

The gear sectors 56 and-32 are'received in the slotted ends of themedial segment !2 by a frictional fit, the coefiicient of friction ofthe nylon material and the surface pressures involved being designedaccording to engineering exigencies in such" amanner that the varioussegments are not. loose uponeach other nor are they so tight that theamputee is unable by the use of his natural' hand to preposition thearticulated finger to any desired angular relationship of which thevarious segments are capable.

From the above description of parts it will be seen that an articulatedfinger has been design d in which there areno protruding levers.linkages or. open slots. The. usual 60 fiexion required at the firstfinger joint has been split into-two. adjacent. 30 fiexions, thusallowing the. provision of a finger with smooth contours and which isfree of open seams and exposed joints.

Although the cosmetic appearance of the nylon.

material is such that a cosmetic glove is notrequired, the amputee may,if he desires, wear a cosmetic glove and in such an instance thecompression and extension required of the cosmetic glove is 'verymaterially reduced.

While there have been shown and described and pointed out thefundamental novel features of the invention. as applied to a preferred,embodiment, it will be understood that various.

omissions and substitutions and changes in the form and details of theapparatus illustrated and in its operation may be made by those skilledin the art, without departing from the spirit of the invention. It isthe intention, therefore, to be limited only as indicated by the scopeof the following claims.

What. is claimed is: 1. In an artificial hand, a frame, an articulatedfinger including a proximal segment, a ,edial segment and a distalsegment, means operatively pivotally connecting said proximal segto saidframe, means pivotally connecting said proximal segment to said. medialsegment, means pivotally connecting said. medial segment to said distalsegment, a gear sector fixedly carried by said proximal segment andprojecting. into said medial segment, a second gear sector fixedlycarried by said distal. segment and likewise projecting into said medialsegment and meshing with saidfirst mentioned gear sector, and a linkhaving one end. operatively pivotally: connected to said frame at apoint eccentric of the connection of said. proximal segment to saidframe and the other end thereof pivotally con nected to said medialsegment at a point on the latter eccentr cally disposed with respect tothe pivotal. axis of connection between proximal se ment and said medialsegment.

2. In an artificial hand, a frame, an articulated finger including aproximal segment, a medial segment and a distal segment, meansoperatively pivotally connecting said proximal segment to said frame,means pivotally connecting said proximal segment to said medial'segment,means pivotally connecting said medial segment to distal segment, a gearsector fixedly carried by said proximal segment and projecting into saidmedial segment, a second gear sector fixedly carried by said distalsegment and likewise projecting into said medial segment and meshingwith said first mentioned gear sector, and a link having one endoperatively pivotally connected to said frame at a point eccentric ofthe connection of said proximal segment to said frame and the other endthereof pivotally connected to said medial segment at a point on thelatter eccentrically disposed with respect to the pivotal axis ofconnection between said proximal segment and said medial segment.

3. In an artificial hand having a frame, an articulated finger for saidhand including a proximal segment, a medial segment and a distalsegment, means operatively pivotally connecting said proximal segment tosaid frame, means pivotally connecting said proximal segment to saidmedial segment, means pivotally connecting said medial segment to saiddistal segment, said segments each being formed of moldable material, agear sector integrally formed on said proximal segment, a second gearsector integrally formed on said distal segment, said medial segmentbeing of hollow shell-like configuration and said gear sectorsprojecting into said medial segment and meshing with each otherinteriorly thereof, and a link operatively pivotally connected at oneend to said frame at a point eccentric to the connection of saidproximal segment to said frame and at the other end to said medialsegment at a point eccentrically disposed with respect to the pivotalaxis of connection between said proximal segment and said medial segmentwhereby pivotal movement of said proximal segment relative to said framewill cause pivotal movement of the medial segment relative to theproximal segment.

4. In an artificial hand having a frame, an articulated finger for saidhand including a proximal segment, a medial segment and a distalsegment, means operatively pivotally connecting said proximal segment tosaid frame, means pivotally connecting said proximal segment to saidmedial segment, means pivotally connecting said medial segment to saiddistal segment, a gear sector integrally formed on said proximalsegment, a second gear sector integrally formed on said distal segment,said medial segment being of hollow shell-like configuration and saidgear sectors projecting into said medial segment and meshing with eachother interiorly thereof, and a link operatively pivotally connected atone end to said frame at a point eccentric to the connection of saidproximal segment to said frame at a point removed from the pivotal axisbetween said proximal segment and the frame and at the other end to saidmedial segment at a point eccentrically disposed with respect to thepivotal axis of connection between said proximal segment and said medialsegment whereby pivotal movement of said proximal segment relative tosaid frame will cause pivotal movement of the medial segment relative tothe proximal segment and pivoted movement of the distal segment relativeto the medial segment.

5. In an artificial hand including a frame, an articulated finger forsaid hand comprising a proximal segment, a medial segment and a distalsegment, said proximal and medial segments each being in the form of ahollow shell, means operatively pivotally connecting said proximalsegment to said frame, means pivotally connecting said proximal segmentto said medial segment, means pivotally connecting said medial segmentto said distal segment, a link having one end pivoted to said frame andthe other end operatively pivotally connected to said medial segmentabout an axis eccentrically disposed with respect tothe axis of pivotalconnection between said proximal and medial segments, the effectivelength of said link being shorter than 6 the distance between thepivotal axis existing between said proximal segment and the frameworkand the pivotal axis existing between the proximal segment and themedial segment whereby swinging movement of said proximal segmentrelative to the framework will effect swinging movement of the medialsegment with respect to said proximal segment, a gear sector fixedlycarried by said proximal segment, a second gear sector fixedly carriedby said distal segment, said gear sectors projecting into said medialsegment and meshing with each other whereby swinging movement of saidmedial segment with respect to said proximal segment will cause swingingmovement of said distal segment with respect to said medial segmentthereby effecting a curling or an uncurling action of the articulatedfinger, as the case may be.

6. In an artificial hand including a frame, an articulated finger forsaid hand comprising a proximal segment, a medial segment and a distalsegment, said proximal and medial segments each being of hollowshell-like configuration, means operatively pivotally connecting saidproximal segment to said frame, means pivotally connecting said proximalsegment to said medial segment, means pivotally connecting said medialsegment to said distal segment, the opposite ends of said medial segmentbeing generally of convex arcuate configuration and each being providedwith a transverse slot therein, the outer end of said proximal segmentbeing generally of concave arcuate configuration with the adjacent endof said medial segment nesting therein with sufficient clearance beingprovided for relative pivotal movements between said two lattersegments, the inner end of said distal segment being generally ofconcave arcuate configuration with the outer end of said medial segmentnesting therein with sufficient clearance being provided to permitrelative movements between said medial and distal segments, a gearsector integrally formed on said proximal segment and projecting intoone of said transverse slots, a second gear sector integrally formed onsaid distal segment and projecting into the other transverse slot, saidgear sectors meshing with each other inside of said medial segments withthe sides of said gear sectors frictionally engaging the edges of theirrespective slots to yieldably hold said segments in predeterminedrelative positions of angularity with respect to each other, a linkoperatively pivotally connected at one end to said frame about an axisremoved from the axis of pivotal connection between said proximalsegment and the frame and at the other end to said medial segment aboutan axis removed from the axis of pivotal connection between saidproximal segment and said medial segment, the effective length of saidlink being less than the distance between the pivotal axis between saidproximal segment and frame and the pivotal axis between said proximalsegment and said medial segment.

LINUS J. PARKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,285,617 Caron Nov. 26, 19181,507,681 Pecorella et al Sept. 9, 1924

